The present invention is directed to communication via a wireless connection and, more particularly, to wireless communication capable of carrying voice and/or data signals at high data rates.
Recent wireless communication systems, such as cellular systems that use code division multiple access (CDMA) technology, often employ a xe2x80x9csoft handoffxe2x80x9d where, at any given time, a mobile station communicates with the network via more than one base transceiver station (BTS). The soft handoff ensures that the mobile station communicates continuously with the network while the mobile station moves across cell regions covered by respective BTSs.
Soft handoff systems, however, are prone to having the transmissions from one BTS interfere with those from another BTS. Also, when such systems are used to transfer data packets, complex scheduling of the routing of the packets is required which often delays the movement of the packets.
To reduce interference and improve the packet transfer speed, cell switching may be employed instead of a soft handoff. In cell switching, only the BTS having the best transmission channel quality is selected to transmit to the mobile station. The mobile station periodically measures the channel quality of each BTS in its active set, typically by measuring the carrier to interference ratio (C/I) of each BTS. When a mobile station that is receiving forward link transmissions from one BTS enters a region where it can receive transmissions from more than one BTS, or when the mobile station that is receiving forward link transmissions from the BTS experiences a reduction in forward link transmission quality because of fading, shadowing or signal path loss, the mobile station then determines which BTS is transmitting at the highest channel quality and sends an indication of the desired BTS, namely the BTS transmitting at the highest channel quality, to each BTS in the active set.
Because the switching from one BTS to another is based solely on the channel quality, a mobile station may be switched from one BTS to another BTS in its active set that is already heavily loaded. As a result, the traffic load is unevenly distributed among the BTSs which results in traffic congestion and transmission delays that degrade the quality of service for some or all of the mobile stations that are served by the heavily loaded BTS.
It is therefore desirable that the mobile stations be switched from one BTS to another in a manner that more evenly distributes the loading of the BTSs. It is further desirable that the switching be driven by a network-side entity so that the loading of the BTSs is centrally controlled.
The present invention provides for fast switching from one BTS to another that is network driven and that is based on the loading conditions of the BTSs that are in the active set as well as being based on the transmission channel quality of the BTSs.
A remote station measures the transmission channel quality associated with base stations in its active set, and the remote station sends the transmission channel quality information stations to a network entity, such as a mobile control point (MCP), at predefined intervals via its current base station. Loading information associated with the base stations is reported to the network entity by the base stations. The network entity selects a respective one of the base stations based on a function of the transmission channel quality information reported by the remote station and the loading information of the base stations. The network entity sends the remote station an indication that it is to commence communication with the selected base station.
In accordance with an aspect of the invention, one of a plurality of base stations is selected by a network entity for communicating with a respective remote station. Transmission channel quality information associated with at least two of the base stations is received at predefined intervals. Loading information associated with the base stations is received at further predefined intervals. A respective one of the base stations is selected as a function of the quality information and the loading information. An indication that the respective remote station is to commence communication with the selected one of the at least two base stations is sent to the respective remote station.